Do you have anything behind the edge router that would be suitable to run a scheduled task or background process on? While it's likely possible to ninja something onto an edgerouter, I don't think you can do it in a way which will survive os updates.

Yes, I could easily do something on the internal network. However, since the router knows when its external address changes, the updates can be synchronous, rather than being based on times checks. In the end, I guess I am looking for an elegant solution rather than an easy one. But, OTOH, fewer parts in a system is always better.

I am not too concerned about router OS updates and can manage that process.

It may be possible for us to support one of the dyndns update protocols that's baked into ubnt's products. That said, a scheduled task that updates DNS if an external IP has changed running every 5 minutes would put no appreciable load on a system and would converge fast enough for most people's needs.

Oh, I totally understand about there load. As I noted, it is really the elegance of simplicity I am looking for. However, having noted that, if you could add support for one of the already supported ubnt supported dynamic dns schemes, that would be a nice plus for users who might not know how to, or be able to, create their own script to deal with the "issue."

It turns out, the Edgerouter won't work in this case (FTTN) because of the AT&T provided router.

However, I have found a third-party developer (https://ddnsbroker.com) who is willing and interested in adding support for Sonic's API into his product for MacOS. All he needs (in his words) is a: ...complimentary developers account for test purposes. Which makes sense.

I can provide the developer's contact info, plus whatever else you need. If you are interested, let me know the best way to get in direct contact with you.

It turns out the AT&T router will not work for the application needed. For that reason it has been switched to IP Passthrough mode and the Edgerouter is again the gateway device and DHCP client for its WAN address.

So, I, once again, began searching for a means to get the Edgerouter to do the Sonic Dynamic DNS updates. And, I think I have found the hook. It is described in this forum post on the Ubiquiti forums. Essentially, after each DHCP update, EdgeOS looks in a specific location for exit scripts to execute. All that is needed is to place an appropriate script in that location. And, in fact, the post's author even provides a sample script.

With this information in hand, I then googled for "edgerouter dynamic-dns dhclient-exit-hooks" and got a lot of hits with other, similar, scripts to do the same thing.

Still untested. But, it looks good.

CAVEATS:

As Kelsey previously warned. Scripts do not persist after an upgrade. You have to re-install them.

You still need a simple script somewhere, could be on the router, to get the authentication token.